//===---------------------------------------------------------------------===//
Missed instcombine transformation:
-define i32 @a(i32 %x) nounwind readnone {
-entry:
- %rem = srem i32 %x, 32
- %shl = shl i32 1, %rem
- ret i32 %shl
-}
-
-The srem can be transformed to an and because if x is negative, the shift is
-undefined. Here's a more general case that occurs on 64-bit targets:
%382 = srem i32 %tmp14.i, 64 ; [#uses=1]
%383 = zext i32 %382 to i64 ; [#uses=1]
%384 = shl i64 %381, %383 ; [#uses=1]
%385 = icmp slt i32 %tmp14.i, 64 ; [#uses=1]
-Testcase derived from 403.gcc.
+The srem can be transformed to an and because if x is negative, the shift is
+undefined. Testcase derived from 403.gcc.
//===---------------------------------------------------------------------===//
if (ConstantInt *CUI = dyn_cast<ConstantInt>(Op1))
if (Instruction *Res = FoldShiftByConstant(Op0, CUI, I))
return Res;
+
+ // X shift (A srem B) -> X shift (A urem B) iff B is positive.
+ // Because shifts by negative values are undefined.
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op1))
+ if (BO->getOpcode() == Instruction::SRem && BO->getType()->isIntegerTy()) {
+ // Make sure the divisor's sign bit is zero.
+ APInt Mask = APInt::getSignBit(BO->getType()->getPrimitiveSizeInBits());
+ if (MaskedValueIsZero(BO->getOperand(1), Mask)) {
+ Value *URem = Builder->CreateURem(BO->getOperand(0), BO->getOperand(1),
+ BO->getName());
+ I.setOperand(1, URem);
+ return &I;
+ }
+ }
+
return 0;
}
; CHECK: %ins = or i128 %tmp23, %A
; CHECK: %tmp46 = trunc i128 %ins to i64
}
+
+define i32 @test38(i32 %x) nounwind readnone {
+entry:
+ %rem = srem i32 %x, 32
+ %shl = shl i32 1, %rem
+ ret i32 %shl
+; CHECK: @test38
+; CHECK-NOT: srem
+; CHECK: ret i32
+}
+